JPH068243Y2 - Cast steel hollow camshaft for valve train of internal combustion engine - Google Patents

Description

Detailed Description of the Invention A. Purpose of the Invention (1) Field of Industrial Application The present invention relates to a cast steel hollow camshaft for a valve train for an internal combustion engine.

(2) Conventional Technology Conventionally, as this kind of hollow cam shaft, one made of cast iron is known (see Japanese Patent Laid-Open No. 59-206141).

(3) Problems to be Solved by the Invention However, when the hollow camshaft is made of cast iron, there arises a problem that strength cannot sufficiently cope with high engine rotation and high output.

Therefore, it has been proposed to configure the hollow camshaft from cast steel, but during casting, if the hollow part molding core is held in the mold by a keren, the molten metal temperature of the cast steel may change depending on the material of the keren and its installation position. It is impossible to provide a hollow shaft having good casting quality due to its high price and poor hot running property.

In view of the above, the present invention has an object to provide the hollow camshaft having good casting quality.

B. Configuration of the Invention (1) Means for Solving the Problems The present invention relates to a cast steel hollow cam shaft for a valve mechanism for an internal combustion engine, which comprises a molybdenum keren holding a hollow molding core in a mold during casting. The constituent part is characterized in that the end face is exposed on the outer surface of the journal and is left in the journal.

(2) Action When cast steel is used as a constituent material as described above, high engine rotation,
Provided is a hollow camshaft that can sufficiently cope with high output.

Moreover, the constituent parts of molybdenum keren are left in the journal.Therefore, keren does not melt or cause thermal deformation depending on the molten metal of the cast steel. Securely held in
On the other hand, keren does not prevent the flow of molten metal because it is placed in the Janal molding region of the mold cavity, which has a relatively large volume, and therefore has good meltability and good casting quality. Will be provided.

In this hollow camshaft, the end surface of the keren component is exposed on the outer peripheral surface of the journal, but the surface pressure acting on the journal during engine operation is low, and therefore the end surface does not become the starting point of scuffing.

In the cavity of the mold, the volume of the cam forming area is the largest, but if the kelen is arranged in the cam forming area and the constituent portion of the kelen is left on the cam, the end surface of the constituent portion is exposed on the outer peripheral surface of the cam. Therefore, there occurs a problem that the end surface becomes a starting point of scuffing due to the high surface pressure acting on the cam during engine operation.

Further, when adjacent parts of the kelen are left in the constricted portions existing between the adjacent cams, between the cams and the journals, the constricted portion forming region of the cavity has a relatively small volume, and therefore a hot-water failure tends to occur. Such a problem occurs.

(3) In the first to fourth diagram embodiment, hollow camshaft for an internal combustion engine for a valve operating mechanism is composed of cast steel, the first to fifth journal 2 ₁ toward the other end from the one end ₂₅ are arranged at a predetermined interval. 1st and 2nd journals 2 ₁ and 2 ₂
Two between them, four between the second and third journals 2 ₂ and 2 ₃ ,
Four cams 3 are arranged between the third and fourth journals 2 ₃ and 2 ₄ and two cams 3 are arranged between the fifth journals 2 ₄ and 2 _{5 at} predetermined intervals.

A hollow portion 4 extending in the axial direction of the hollow camshaft 1 is formed. One end of the hollow portion 4 is closed by an end wall 5 of the first journal 2 ₁ side, and the other end is open to the fifth journal 2 ₅ of the end.

The second, third, and fourth journals 2 ₂ , 2 ₃ , 2 ₄ are provided with molybdenum keren constituent parts a ₁ , a ₂ , a ₃ for holding the hollow part molding core in the mold during casting. Both end surfaces b are exposed and left on the outer peripheral surfaces of the respective journals 2 ₂ , 2 ₃ , 2 ₄ .

The hollow camshaft 1 is cast using a casting device 6 shown in FIGS.

The mold 7 is a shell type, and includes an upper mold 8 and a lower mold 9. The gate 10 is defined by the mating surfaces of both molds 8 and 9,
The gate 10 communicates with one end of a similarly defined camshaft forming cavity 11.

A hollow part molding core 12 is disposed in the cavity 11,
The core 12 is held in the mold 7 as follows.

A skirting board 13 is continuously provided on the core 12 on the side opposite to the side where the gate 10 is present, and the skirting board 13 is sandwiched between the upper and lower molds 8 and 9.

Substantially longitudinal center portion is held in the mold 7 via the first Keren 14 _1, and the second to prevent Ri floating of both longitudinal end portions side core 12 of the core 12 of the core 12, the third Keren 1
4 through _2, 14 ₃ is held in the mold 7.

Each of the kerens 14 _{1 to} 14 ₃ is formed by using a wire of molybdenum (melting point: 2625 ° C.) having a diameter of 1.8 mm,
The semi-circular holding portion 14a and a pair of linear mounting portions 14 that are bent and formed so as to project in opposite directions from both ends thereof.
b.

In the core 12, a semi-annular first groove 16 ₁ opening downward is formed in the third journal forming portion 15 of the core 12, and the second and fourth semi-annular grooves 16 ₁ are formed.
Semi-annular second and third grooves 16 ₂ and 16 ₃ that open upward are formed in the journal forming portions 17 and 18, respectively.

As shown in FIG. 6, the first Keren 14 ₁ of the holding portion 14a
Is fitted in the first groove 16 ₁ of the core 12, and each mounting portion 1
4b is a pair of mounting grooves 1 on the mating surfaces of the two molds 8 and 9.
It is sandwiched between 9 and 20. As shown in FIG. 7, the second Keren 14 _second holding portion 14a is fitted in the second grooves 16 _{and second} core 12, and each attachment portion 14b, each lies in the mating surface of the dies 8 and 9 It is sandwiched between the pair of mounting grooves 19 and 20. Third Keren 14 _3, a relative mold 7 and cores 12 2
It is arranged similarly to Keren 14 _2.

Therefore, the first barrel 14 ₁ is the third cavity of the cavity 11.
The journal forming regions 11a, also in the second journal forming region 11b of the second Keren 14 ₂ cavities 11, further third Keren 14 ₃ are respectively disposed in the fourth journal forming region 11c of the cavity 11.

As the cast steel, one having the composition shown in the table below is used.

The balance contains additional impurities.

The molten metal of the cast steel is poured into the cavity 11 through the gate 10 at 1500 to 1550 ° C. to cast the hollow camshaft 1.

At the time of this casting, since each of the keles 14 _{1 to} 14 ₃ is not melted by the molten metal or thermally deformed, the core 12 is reliably held in a predetermined position in cooperation with the skirting board 13, while each of the kelenes 14 _{1-14 3} relatively since volume is disposed in the larger second to fourth journal forming region 11a~11c of without prevent the metal flow and thus a molten metal property Yoshiko, a wall thickness uniformity Hollow camshaft with good casting quality 1
Is obtained.

In the hollow camshaft 1, the second to fourth journals 2
The protruding portion of each mounting 14b protruding from _{2 to} 2 ₄ is cut off, and thus each journal 2 ₂ to 2 ₄ as described above.
On the outer peripheral surface, the constituent parts a of the kerens 14 _{1 to} 14 ₃ are formed.
Although both end faces b of ₁ ~a ₃ is exposed, during engine operation, the surface pressure acting on each journal 2 ₂ 21 to ₂₄ is low, thus there is no possibility that they end face b is starting points of scuffing.

As described above, when each of the kerens 14 _{1 to} 14 ₃ is made of a molybdenum wire, not only can the heat resistance of each of the kerens 14 _{1 to} 14 ₃ be improved, but the wire is a high melting point metal, It also has the advantage of being relatively easy to use.

The diameter of the molybdenum wire is preferably 1.5 mm or more. As a result of the experiment, those with diameters of 1.5, 1.8, 2.0, and 2.6 mm do not cause thermal deformation, but if the diameter is less than 1.5 mm, thermal deformation occurs, so that the core 12 moves and the wall thickness of the hollow camshaft 1 increases. Becomes uneven.

The diameter used to cast the cast iron hollow camshaft
A 0.8 to 2.0 mm mild steel wire is unusable because it is melted by the molten cast steel. In this case, no improvement can be seen even if the wire is subjected to surface treatment such as chrome plating. on the other hand,
If the diameter of the mild steel wire is set to, for example, 4.0 mm or more, problems such as melting and thermal deformation of the wire are solved, but the depths of the _first to third grooves 16 _{1 to} 16 ₃ of the core 12 are increased. , Core 12
Each of the journal molding portions 15 to 18 is easily damaged during casting, and the flow of molten metal is prevented, resulting in defective running.

The alloy element-containing wire rod, for example, a stainless steel wire rod (for example, JIS SUS304, 430, 410) is thermally deformed.

Wires made of titanium, chromium, tungsten, nickel, etc. are not suitable as wire rods for keren because they are expensive and have poor workability such as press molding.

Further, the ceramic wire rod has problems that it is easily broken due to its low impact resistance, it is difficult to remove it from the hollow cam shaft, and a kerlen removal hole is formed in the hollow cam shaft.

As the mold 7, in addition to the shell mold, a differential pressure molding mold, a self-hardening mold, a lost wax method, a show process, or the like is used.

C. Effect of the Invention According to the present invention, it is possible to provide a cast steel hollow camshaft having good casting quality, which can sufficiently cope with high engine rotation and high output.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention, FIG. 1 is an overall vertical sectional front view, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG.
FIG. 2 is a view taken along the line IIa in FIG. 3, FIG. 3 is a sectional view taken along the line III-III in FIG. 1, FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1, and FIGS. 5 is a vertical sectional front view of the whole, FIG. 6 is a sectional view taken along line VI-VI of FIG. 5, and FIG. 7 is a sectional view taken along line VII-VII of FIG. 1 ... hollow _{camshaft 2} 1 to 2 5 _... first to fifth journal, 3 ... cam, 4 ... hollow portion, 7 ... mold, 12 ... core,
14 _1-14 3 _... first to third _{Keren, a} 1 ~a 3 _... component, b ... end surface

Claims (1)

[Scope of utility model registration request] 1. A cast steel hollow camshaft for a valve mechanism for an internal combustion engine, wherein a molybdenum keren component that holds a hollow molding core in a mold during casting has its end face on the outer peripheral surface of the journal. A cast steel hollow cam shaft for a valve train for an internal combustion engine, which is exposed and left in the journal.